Does a left bundle branch block (LBBB) on an electrocardiogram (EKG) require referral to a cardiologist for preoperative evaluation?

Preoperative Cardiology Referral for Left Bundle Branch Block on EKG

A patient with left bundle branch block (LBBB) on preoperative EKG should undergo pharmacologic stress testing rather than routine cardiology referral, unless there are additional cardiac risk factors or symptoms present.

Assessment of LBBB in Preoperative Evaluation

LBBB on EKG alone is not an automatic indication for cardiology referral before noncardiac surgery. The approach should be guided by:

Risk Stratification Considerations

• LBBB without symptoms or risk factors: Does not require routine cardiology referral for low to moderate-risk surgeries 1
• LBBB with cardiac symptoms or risk factors: Warrants further evaluation before elevated-risk surgeries 1

Diagnostic Challenges with LBBB

LBBB presents specific diagnostic challenges that influence preoperative management:

• LBBB masks ECG diagnosis of left ventricular hypertrophy and interferes with ischemia detection 2
• Exercise stress testing has poor specificity (33%) and diagnostic accuracy (36-60%) in patients with LBBB 1
• LBBB may be associated with underlying coronary artery disease (CAD), particularly involving the left anterior descending artery 3

Recommended Approach

For Asymptomatic Patients with LBBB:

1. Obtain baseline 12-lead ECG for patients undergoing elevated-risk surgeries to establish a baseline and guide perioperative management 1
2. No routine cardiology referral needed if:
   • No symptoms of cardiovascular disease
   • No additional cardiac risk factors
   • Low-risk surgical procedure planned 1

For Patients with LBBB and Additional Risk Factors:

If the patient has LBBB plus any of:

• Known coronary heart disease
• Significant arrhythmia
• Peripheral arterial disease
• Cerebrovascular disease
• Structural heart disease
• Symptoms of cardiovascular disease
• Elevated-risk surgery planned

Then:

1. Pharmacologic stress testing is preferred over exercise stress testing 1

   • Vasodilator stress (dipyridamole or adenosine) perfusion imaging has superior diagnostic accuracy (88-92%) compared to exercise testing 1
   • Dobutamine stress echocardiography is also appropriate with diagnostic accuracy of 87% 1

2. Avoid exercise stress testing as it yields false-positive results in LBBB patients 1

3. Avoid combining exercise with dipyridamole or using synthetic catecholamines as these yield false-positive results 1

Special Considerations

• Mortality risk: Some evidence suggests patients with LBBB may have increased perioperative mortality risk compared to those with right bundle branch block or no conduction abnormalities (OR 6.0,95% CI 1.2-100.0) 4

• Diagnostic accuracy: For detection of LAD ischemia in LBBB patients, dobutamine stress echocardiography and perfusion imaging have similar diagnostic sensitivity (83% vs 75%) and identical specificities (92%) 1

• Underlying pathology: LBBB may be the first manifestation of more diffuse myocardial disease, with common etiologies including idiopathic/degenerative causes (52.6%), atherosclerotic coronary artery disease (31.5%), and cardiomyopathies (15.7%) 3, 2

Conclusion

The presence of LBBB on preoperative EKG does not automatically necessitate cardiology referral before noncardiac surgery. The decision should be based on the presence of additional cardiac risk factors, symptoms, and the risk level of the planned surgery. When further cardiac evaluation is indicated, pharmacologic stress testing is the preferred approach rather than exercise stress testing.